Investigation into the effect of subcooling on the kinetics of hydrate formation

Mali, Gwyn Ardeshir; Chapoy, Antonin; Tohidi, Bahman

doi:10.1016/j.jct.2017.08.014

Cited by 32 publications

(20 citation statements)

References 17 publications

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“…Among the many benchtop testing set-ups, the conventional rocking cell has been extensively used for LDHI qualifications by the oil and gas industry. ,, The rocking cell continuously moves by a rocking motion, and the fluid contents in the cell are mixed by the motion of a solid steel ball. However, a large gap between the testing conditions of the rocking cell and the actual flow conditions in the field is caused by the rolling ball, which moves together with the fluid, breaks up the hydrates formed in the tube, and pushes them to accumulate at the end of the cell .…”

Section: Resultsmentioning

confidence: 99%

Advancing Laboratory Characterization and Qualification of Additives for Hydrate Slurry Flow in Multiphase Systems

Sum

2020

Ind. Eng. Chem. Res.

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In the flowlines of oil/gas production systems, the formation of gas hydrates, icelike crystalline compounds of water and gas that form at low temperature and high pressure, can disrupt stable flow, often resulting in solid blockages that necessitate remediation and pose safety issues. Low dosage hydrate inhibitor antiagglomerants (LDHI-AAs) are chemical additives used to manage the hydrate slurry flow at relatively low dosage (∼1% of water content) by dispersing hydrates in the continuous liquid hydrocarbon phase. A reliable assessment of LDHI-AA performance is thus required for their optimal use under a given field condition. Rocking cells have been extensively used in the oil/gas industry for LDHI-AA qualifications as it is easy to build and allows full visualization of the cell interior. However, a solid rolling ball, which is put into the conventional rocking cell for mixing, brings significant disturbances to the flow and dispersion of the phases and, in particular, by breaking up the hydrates formed and pushing them to accumulate at the end of the cell, giving a very conservative (worst-case) evaluation of LDHI-AAs. There is a large gap between the testing conditions of rocking cells and the actual field conditions. The recently developed rock-flow cell can provide a much closer representation of the shear, phase dispersion and thus the flow regime in flowlines. Here, we demonstrate the capability of the rock-flow cell as a more robust testing tool for LDHI-AA qualification. The impact of the cooling mode, degree of subcooling, and salinity are well characterized in terms of hydrate aggregation, deposition, and bedding. The test results demonstrate the advantages of the rock-flow cell over the conventional rocking cell to characterize the hydrate slurry by visualization and quantification of the hydrate formation and accumulation. As such, the rock-flow cell can be used as an effective testing tool for LDHI-AA qualification, which can also be applied to many other phase precipitation problems encountered in flow assurance.

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Section: Resultsmentioning

confidence: 99%

Advancing Laboratory Characterization and Qualification of Additives for Hydrate Slurry Flow in Multiphase Systems

Sum

2020

Ind. Eng. Chem. Res.

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“…While being a smart process for evaluating LDHIs, this method starts forming a preformed hydrate, which is a condition known to reduce the intrinsic stochasticity of hydrate formation. Finally, some groups have studied temperature ramping, but the experimental setups were quite different from ours. , A detailed overview of those and other methods for evaluating LDHIs can be found in the recent literature. − …”

Section: Introductionmentioning

confidence: 99%

Hydrate Induction Time with Temperature Steps: A Novel Method for the Determination of Kinetic Parameters

et al. 2019

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Gas hydrate formation usually occurs with a certain delay after a system composed of water and a hydrate-forming gas is put under suitable thermodynamic conditions of pressure and temperature. This delay period is called the “induction time”, and because of its large variability within a single experimental setting, hydrate formation is often referred to as a stochastic process. The evaluation of induction times, together with other measurements, is taken as an indication for the efficiency of hydrate inhibitors, and they are usually carried out by simply putting the experimental system under chosen P/T conditions and then waiting for the hydrate to form and measuring the time elapsed. In this paper, we present an improved procedure by which the variability of hydrate induction times can be remarkably reduced, while keeping a good correlation of measured induction times with the respective temperatures as obtained by a constant cooling method. In this procedure, temperatures are lowered by 0.5 °C after each time span of 3 h with no hydrate formation. Induction times obtained in this way show a remarkably lower coefficient of variation as compared to a standard induction time measurement.

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“…Zhang et al [42] investigated the influence of varying temperatures during MH formation in water (i.e., in the absence of a porous medium) and the associated gas consumption under a constant pressure mode, but the applicability of his results to core studies is questionable. More recently, the effect of sub-cooling on the formation of natural gas hydrate was investigated by Mali et al [43], but their work focused on nucleation (i.e., on the evolution) of hydrates, did not consider any later-time hydrate behaviour and its kinetics and did not involve a porous medium, making it practically irrelevant to core studies.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

et al. 2019

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Laboratory-created samples of methane hydrate (MH)-bearing media are a necessity because of the rarity and difficulty of obtaining naturally-occurring samples. The hypothesis that the inevitable heterogeneity in the phase saturations of the laboratory samples may lead to unreliable and non-repeatable results provided the impetus for this study, which aimed to determine the conditions under which maximum uniformity can be achieved. To that end, we designed four experiments involving different multi-stage cooling regimes (in terms of their duration and number of stages) to induce MH formation under excess-water conditions. In the absence of direct visualization capabilities, we analysed the experimental results by means of numerical simulation, which provided high-resolution predictions of the spatial distributions of the phase saturations in the cores and enabled the estimation of the parameters controlling the kinetic MH-formation behaviour through history-matching. Analysis of the numerical results indicated that, under the conditions of the experiments and with the design of the reactor, significant heterogeneities in phase saturation distributions were observed in all cases, leading to the conclusion that it is not possible to obtain cores with uniform phase saturation. Additionally, contrary to expectations, heterogeneities increased with the number of cooling stages and the duration of cooling, and this was attributed to imperfect insulation of the upper part of the reactor. A set of simulations involving perfect insulation of the reactor top confirmed the validity of this assumption: (a) predicting the formation of high-uniformity MH-bearing cores that became more homogeneous as 1 The short version of the paper was presented at ICAE2018, Aug 22-25 (2018), Hong Kong. This paper is a substantial extension of the short version of the conference paper.2 the number of cooling stages and the length of the cooling period increased; and (b) providing important information for the improvement of the standard design of the experimental apparatus for the laboratory creation of MH-bearing cores using the excess water method.

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Investigation into the effect of subcooling on the kinetics of hydrate formation

Cited by 32 publications

References 17 publications

Advancing Laboratory Characterization and Qualification of Additives for Hydrate Slurry Flow in Multiphase Systems

Advancing Laboratory Characterization and Qualification of Additives for Hydrate Slurry Flow in Multiphase Systems

Hydrate Induction Time with Temperature Steps: A Novel Method for the Determination of Kinetic Parameters

Effectiveness of multi-stage cooling processes in improving the CH4-hydrate saturation uniformity in sandy laboratory samples

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